There is no "Raggett:" representation as such since the whole
point of the approach I am recommending is that the surface
syntax is malleable and that the linked rule base defines
how to map this to the display schema and clipboard formats.
As a result the examples below are purely subjective:
1) x sub 1 or x_1
2) s sub i sub j or x sub {i sub j}
3) x squared or x sup 2
4) x sub 1 sup 2
My personal bias is towards syntax which matches the way
most people would say the expression aloud.
Dave Raggett